Why not just have Fabspeed weld in their X-pipe? You coudl save your X pipe and just have it reinstalled..... The Fabspeed X-pipe is freer flowing since there are no cats and resonators, and the pipe is not squished and flattened like the BMW pipe. I was under my car yesterday (we installed the AA pulley) and I noticed a lot of flattened areas in the stock X.

Still costs a lot more money than what I'm doing. Plus I want the resonators to remain, they don't cost any power and should help eliminate any drone and keep it from being to raspy sounding. I know the OEM has quite a few squished and flattened spots, but I'm not expecting much difference in HP by eliminating that. My main concern with this mod is better sound, any added HP by losing the secondary cat restriction will just be an added bonus.